The juxtaglomerular apparatus (JGA) is located near the glomerulus and is formed by macula densa cells, extraglomerular mesangial cells, and juxtaglomerular cells. The JGA regulates blood flow and the glomerular filtration rate through secretion of hormones like renin and prostaglandins and via the tubuloglomerular feedback mechanism. The tubuloglomerular feedback mechanism involves macula densa cells detecting NaCl concentration in the renal tubule and secreting adenosine to constrict the afferent arteriole, which decreases glomerular blood flow and filtration rate.